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Biomedical subjects

A Krajewski

Publications and source records attributed to A Krajewski.

At least 19 recordsLinked to original sources
PubMed1997

Cell growth on cordierite: an approach to the identification of reliable supports for continuous-flow solid-bed reactors.

This study aimed to assess the biocompatibility of two cordierite ceramics (DF and Cord 1014), with similar chemical composition and different porosity, as a potential support for cell growth in a continuous-flow, solid-bed reactor. The Chinese hamster ovary (CHO) cell line transfected with HBV-DHFR recombinant plasmid was seeded on cordierite or polystyrene dishes and evaluated for cell growth and production of recombinant hepatitis B surface antigen. Proliferation of the CHO cells, in terms of cell number, was generally similar in polystyrene and Cord 1014 and always lower in DF. Flow cytometric analysis showed no difference in cell cycle distribution for cells grown on different supports, and showed a two-fold increase in percentage of debris for cells grown on DF than for those grown on Cord 1014 and polystyrene culture dishes. Moreover, the morphology of cells grown on Cord 1014 did not change during the experiment, and cells were well spread and organized. Finally, total recombinant hepatitis B surface antigen production was higher on Cord 1014 than on polystyrene and DF samples. Such evidence suggests that Cord 1014 could be a promising support for growing cells in a continuous-flow, solid-bed reactor.

Animals↗
PubMed1996

Albumin adhesion on some biological and non-biological glasses and connection with their Z-potentials.

Evaluating the properties of absorption of albumin on the surface of biomaterials is an important matter in developing information in the field of biomaterials, since it is the most abundant protein present in the human body and it is an any case the first protein that rapidly flows in quantity in a damaged area of a tissue. This study has taken into consideration three different biological glasses and the results were compared with those coming from three different biologically inert glasses. The values obtained were also compared with those coming from the measurements of the Z-potential of the same glasses to verify if a correlation between albumin absorption and Z-potential of the glasses exists. Both types of measurements were carried out at two different pH values: 4.5 and 7.4. These values were selected since the first may be indicative of an acid environment to simulate that of macrophagic action (other than of inflammatory states) and the second simulates the normal condition of a tissue like healthy bone.

Absorption↗
PubMed1996

Mineral evolution of bone.

A study on the evolution with age of the mineral composition of bones was performed on samples belonging to human and other common mammalian species (cattle, sheep, dog). The study was carried out on the ashes obtained by calcination of the bone samples (1 h at 900 degrees C). The calcined powders were carefully examined by X-ray diffraction, from which precise quantitative evaluation (also confirmed by chemical analysis) of the crystalline phases present was derived. These data were analysed as a function of the introduced fractional age phi, a new relative scale that allows even largely different lifespan species to be compared. An overall linear increase in (Ca + Mg)/P ratio with log phi was found and the other considerations on molecular constitution (especially as regards Mg2+ substituting for Ca2+ in very young subjects) of the various phases detected were formulated and relative implications evaluated. The results appear promising for an improvement of knowledge in the field of biomedical experimentation and clinical implantology.

Absorptiometry, Photon↗
PubMed1993

Transcranial Doppler assessment of the cerebral circulation during postprandial hypotension in the elderly.

OBJECTIVE: The aim of the present study was to evaluate whether alterations in postprandial hemodynamics in the elderly were associated with changes in cerebral perfusion assessed by transcranial Doppler ultrasonography. DESIGN: Time series, ie, post-intervention compared to pre-intervention with no-intervention controls. PARTICIPANTS: Ten elderly institutionalized subjects (4 women, 6 men, mean age 84.9 years). Three subjects had a history of syncope. SETTING: A 725-bed academic long-term care facility. INTERVENTION: A 400-kcal mixed meal. MEASUREMENTS: Heart rate, blood pressure, and blood flow velocity in the middle cerebral artery by transcranial Doppler recording, before the test meal and at 5-minute intervals for 60 minutes afterwards. RESULTS: Systolic, diastolic, and mean arterial blood pressure declined significantly from baseline between 30 and 55 minutes after the meal (P < 0.05, ANOVA); however, maximum and mean blood flow velocity did not change. The pulsatility index (end diastolic to peak systolic amplitude divided by mean velocity) increased significantly (P < 0.05, ANOVA) between 30 and 55 minutes after the meal, suggesting increased arteriolar resistance. There were no significant changes in blood pressure, blood flow velocity, and pulsatility index during a control study conducted with four subjects under identical conditions but without a meal. CONCLUSIONS: The results of this study suggest a small, unexpected increase in resistance of the intracranial circulation following a meal in elderly people with postprandial hypotension. Although the clinical significance of this finding is not known, the occurrence of postprandial arteriolar vasoconstriction may lead to cerebral ischemia during periods of marked blood pressure decline.

Aged↗
PubMed1992

Interface between hydroxyapatite and mandibular human bone tissue.

Samples from intraosseous dental implants, removed from patients for mechanical failures, were examined to analyse the interaction between hydroxyapatite as plasma sprayed coating on titanium supports and human bone. The implantation time varied up to 8 years. No failures had arisen from problems at the interface between the hydroxyapatite coating and bone. The number of samples examined and the implantation times give good statistical conclusions. Histological and microchemical studies showed the good performance and compatibility of this sprayed hydroxyapatite. We present evidence from the best samples which show close bonding with the surrounding bone tissue. New bone is seen all around the coated implant. The composition of the calcium phosphate deposited on the hydroxyapatite and cellular approach were determined, and demonstrate the efficiency of the interaction between this plasma sprayed hydroxyapatite and the bone.

Adhesiveness↗
PubMed1991

Karyotypic abnormalities and immunoglobulin gene rearrangements in Hodgkin's disease.

Biopsy samples from seven patients with Hodgkin's disease (HD) were examined for cytogenetic abnormalities and rearrangement of the genes encoding the immunoglobulin chains and T-cell receptor chains. Three samples demonstrated clonal rearrangements of both IgH and IgL genes. No rearrangements of the TCR beta genes were detected in any of the samples. Karyotypic abnormalities were also found but only in the three cases where a clonal rearrangement of the immunoglobulin genes was shown. Two of these three cases had multiple karyotypic abnormalities, with the remaining patient being trisomic for chromosome 16 as the sole abnormality. These results are discussed and compared with previous reports in the literature concerning HD.

Adolescent↗
PubMed1990

Clinical significance of carotid plaque hemorrhage.

We correlated the clinical and pathologic findings in 77 consecutive carotid plaques removed at endarterectomy to determine the clinical role of intraplaque hemorrhage. Intraplaque hemorrhages of various severity were seen in 86% of plaques. They were, for the most part, deeply located (63%) and infrequently connected with the lumen. They related closely to the severity of carotid stenosis, but bore no relationship to the timing of symptoms. Luminal thrombus was infrequently seen, and was always microscopic. Hemorrhage into carotid plaque appears to represent an index of the severity of the stenosis and plaque instability rather than to play a direct role in the pathogenesis of transient ischemic attacks or stroke.

Aged↗
PubMed1990

In vitro observations of iron-doped bioactive glasses.

Several in vitro tests are necessary to evaluate the biological compatibility of materials used to manufacture implants for humans or animals. These tests will indicate whether these materials can be tolerated when implanted in vivo. Since ceramic materials are suitable for coating layers, it was decided to study their performance by adding certain oxides as doping agents. This paper describes their influence in vivo in some preliminary tests and in vitro for iron trioxide only. This work attempts to ascertain the range of doping to maintain the bioactivity characteristics and in particular the influence of iron trioxide as a doping agent in the bioactive glass. To do so the adhesion of baby hamster kidney cells to bioactive glasses doped with different concentrations (2 and 4 wt%) of this compound was quantified. The base glass without iron oxide was used as a control as 0 wt% doping. In a second phase, a coating of fibronectin, a glycoprotein that plays an important role in cell binding and spreading on substrates, was quantified on the same surfaces. It was shown that the cell avidity for the surfaces of the materials increases with increased doping of iron oxide. The values are significantly higher than those observed for the base glass. Fibronectin adsorption quantification showed a similar trend, with values of adsorption similar for the doped samples and higher than that of the non-doped glass. It was demonstrated that iron trioxide induces an increase in cell adhesion capability with bioactive glass surfaces and the capability of adhesion of the fibronectin to act as a substrate on the same surfaces.

Adsorption↗
PubMed1990

The clinical role of the cerebral collateral circulation in carotid occlusion.

The occurrence and severity of ischemic cerebral symptoms after carotid occlusion depends on the interdependency of cerebral collateral blood supply. Only those with the "fittest" collateral capacity survive this process of natural selection. Using the transcranial Doppler method in 55 patients with unilateral carotid occlusion, we tested the dependency of each cerebral hemisphere on the remaining patent carotid artery by digital carotid compression, and in 41 of these patients we also tested the carbon dioxide reactivity in each hemisphere. Both hemispheric dependency and carbon dioxide reactivity were compared to 15 healthy controls. Mean blood flow velocities in the middle cerebral artery were lower on the occluded side than on the patent side (p less than 0.003). When the patent carotid artery was compressed middle cerebral artery blood flow velocities on the occluded side were mainly independent of the patent carotid artery, but on the patent side there was a high degree of dependency (p less than 0.0001). Carbon dioxide reactivity did not differ between the hemispheres, but in hemispheres with total dependency, carbon dioxide reactivity was inversely proportional to the severity of stenosis (r = -0.63). Tests of cerebral collateral reserve in patients with unilateral carotid occlusion evaluated by carotid compression and cerebral carbon dioxide reactivity may discriminate between survivors and potential nonsurvivors before the patent carotid artery occludes.

Aged↗
PubMed1990

The cluster diathesis.

We present further evidence for a sympathetic defect of vasomotor control of the anterior cerebral artery (ACA) on the side of the headache during cluster periods. In 119 cluster headache patients, utilizing transcranial Doppler, we measured CO2 reactivity of the major intracranial vessels, in and out of cluster. Reactivity was significantly lower during the cluster period, but only in the ACA on the side of the headache. Nineteen patients followed sequentially for a full cycle (ie/both in and out of a cluster period) showed the same changes. In 3 out of 6 patients in an active cluster period, we describe a lesion on Gallium single-photon emission computerized tomography (SPECT) in the region of the cavernous sinus which fades as the patient moves out of cluster. It is felt that this lesion may represent the cavernous sinus plexus lesion postulated as the central lesion in cluster. Changes in the sympathetic outflow at this point could explain the changes we have described in ACA CO2 reactivity during cluster.

Adult↗
PubMed1990

Comparative analyses among interfaces of some ceramic materials and bone in sheep.

Aim of this work is the evaluation of "in situ" implants in an animal model to study the interfaces that some ceramic materials for dental bone defects develop with bone and to check which material is more osteoconductive. In a sheep's jaw, eight holes were drilled and filled with six ceramic materials in granular shape. Two bilateral holes were left empty as reference. The ceramic materials were: porous tricalcium phosphate (TCP), porous hydroxylapatite (HA) and four bioactive glasses. The glasses differ for doping agents that affect the velocity of biodegradation in the living body. Monthly radiographs were taken and the X-ray pictures analyzed by means of a Video Display Computer in order to quantify the optical density changes occurred in the holes. After 4 months implantation, the segments of the jaw containing the materials were fixed in paraformaldehyde, embedded in methylmethacrylate and sectioned. The results obtained under the microradiograph, the SEM and the X-ray microprobe showed a good bone repair only with TCP granules. A great degradation was seen in HA granules and particularly in glasses. The degradation modified the structure and the composition of the glass granules, but it was not followed by a consequent bone deposition.

Animals↗
PubMed1989

Reversal of cluster headache side following treatment of arteriovenous malformation.

We describe the case of a forty-four year old man who had typical right sided cluster headaches and an arteriovenous malformation supplied mainly by the right anterior cerebral artery. Following endovascular embolisation of this artery the AVM was supplied mainly by the left anterior cerebral artery. Subsequent headaches have always been on the left. Transcranial Doppler studies now suggested an increase of middle cerebral artery flow velocity. We suggest that the change in haemodynamics was responsible for the change in headache side.

Adult↗
PubMed1988

Mineralization and calcium fixation within a porous apatitic ceramic material after implantation in the femur of rabbits.

Cylinders (0.8 cm long, 1.0 cm of diameter and with an axial hole), constituted, after firing, of a ceramic mixture of hydroxylapatite (HA) and beta-tricalciumphosphate (beta-TCP) in a 10:1 ratio, were implanted into mid-diaphyseal defects of one femur of 20 rabbits and stabilized with intramedullary rods. The implantation sites were checked radiographically every month, and after 3 months (3 animals) and 6 months (17 animals) the rabbits were sacrificed and the implants with the surrounding tissue were embedded in methylmethacrylate, cut to thick sections and analyzed by scanning electron microscopy (SEM). Porosimetric and x-rays diffraction analyses were carried out before and after implantation of the cylinders, and the state of mineralization at the bone-implant interface was determined by EDAX microprobe analysis. Bony callus formation started at 1 month at the osteotomy sites, as judged by radiography, but after 3 months a not-mineralized zone had still been demonstrated between bone and the implants. At 6 months, 13 implants showed themselves firmly fixed in their implantations beds, while 4 implants were only incorporated at their proximal ends. In bone contact zones, an enrichment of Ca2+ was displayed by microanalytical techniques in the outer zone of the implanted samples which may be explained by an apparent additional phase transformation of HA into TCP, thanks to the change of the Ca/P ratio, that takes place in vivo.

Animals↗
PubMed1988

Interpretation of difficulties in the initial adhesion of bio-active glasses to bone.

The authors propose a model to explain the initial difficulties in achieving adhesion between bio-active glasses and bone. It is explained that in vitro tests involve biophysical situations which are different, and in many cases very different, from those which take place in in vivo implantation. The model suggests procedures which could be applied to bio-active glasses after the manufacturing process in order to improve their initial adhesion to bone.

Animals↗
PubMed1988

Structural modifications and biological compatibility of doped bio-active glasses.

The Raman laser and infrared spectra of doped bio-active glasses of the 45S5 type are presented and discussed. The spectroscopic results show that the doping agents cause the destruction of the basic glass structure and the consequent formation of SiO4(4-) units in the glass network. When the doped glasses have been immersed in a physiological solution (199 medium), a film of calcite forms on the glass surface and this modification is related to the type of doping agent used, decisive for close linking between metal supports and the glass. The presence of doping agents does not prevent the normal growth of the bone onto the surface of doped bioactive glasses. Histological tests show that tissue response to very fine powders of doped glasses increases up to 15 days more or less according to the structural modifications revealed by spectroscopic measurements.

Animals↗